The Continuity of Life: Genetics and Evolution Selective Breeding
Over thousands of years, humans have changed plants and animals through careful breeding to improve their useful characteristics. This is known as artificial selection because the changes do not take place naturally.
For example:
z Breeding programmes are common in the livestock industry, where cows are bred to produce large volumes of milk and beef.
z The racehorse industry develops traits such as speed, hurdling ability and endurance.
z All dogs are descended from the grey wolf. Hundreds of breeds of domestic dog have been bred over the last 15,000 years or so.
Fig. 4.2.7 Racehorses are selectively bred for speed and endurance
4.2
Grey wolf (common ancestor)
Fig. 4.2.8 All dog breeds are descended from the grey wolf
